Superoxide dismutase catalyzes the conversion of superoxide radicals (O2−) into molecular oxygen (O2) and hydrogen peroxide (H2O2). The conversion of superoxide radicals is generally beneficial to a cell, since such molecules can react with the cell's genomic DNA to induce mutations.
Superoxide dismutases (SOD) have been classified based on the inorganic atoms they require for activity. Three SOD families have been identified: those requiring manganese (MnSOD), those requiring iron (FeSOD), and those requiring copper and zinc (Cu, ZnSOD).
MnSODs have been found in mitochondria and prokaryotes, whereas FeSODs have been found in prokaryotes, primitive eukaryotes, and some plants. Cu, ZnSODs were originally found in eukaryotes and later found in several bacteria.
Macrophages are an important arm of a vertebrate's immune system. Such cells can kill pathogens such as bacteria by engulfing the pathogen and bombarding it with superoxide radicals. Therefore, a secreted Cu, ZnSOD may play a role in the survival of bacterial pathogens, especially those known to survive and grow in macrophages.